Growth hormone deficiency (GHD) and secretory insufficiency are major causes of growth failure and consequent severe short stature. While central nervous system dysfunction accounts for most cases of GHD, specific genetic defects in the GH secretory apparatus can also be responsible, especially when GHD occurs in families. We will define a pool of affected individuals by appropriate endocrine screening studies, test for association with GHRHR and other candiate genes, identify regions of the human GHRHR gene most likely to have phenotypically significant mutations and then screen for such mutations and we will examine leukocyte mRNA for low level transcription of GHRHR gene which could be exploited for mutation analysis.